Just has a week long fight with this circuit. First I beardboarded it and it worked great, then I built it with a pcb. It worked perfect with just a trigger, generating a nice A/D response, controls all working, ditto with just a gate signal, for a nice A/R response. But do you think the gate and trigger would play nice together, no way! I had no attack and very erratic behaviiour from the circuit. Finally replaced the 470pf cap (very old) on the trigger input with a .01uf (new) and now it works 100%. I think the problem was the old cap and the soldering process, I could see a poor trigger on the scope and a much better one with the new cap. Anyway I am very happy now and learned a lot. My only question would be, do I leave the .01uf cap in, or replace it with the correct value? How does Thomas come up with such a value anyway?

How did I pick the value? In a nutshell: rule of thumb. I didn't calculate anything here.

A keyboard trigger is on the order of 5mS. I wanted something much narrower than that to fire the 555. C1 and R5 set a much shorter time constant, guaranteeing the 555 fires pronto.

The circuit should work well with the values shown with just about any keyboard. I suppose it's possible your keyboard may generate a pulse width that made the larger value necessary. And as you say, it's also possible the original cap was cruddy.

If it were me, and given how cheap caps are, I'd try the original value, or maybe a 0.001. But the 0.01 sounds kind of big to me.

Did you design your own PCB for the ADSR? Would you be willing to share it with us? I've been wanting to build this one, along with the 2164 VCA (doubled up for good measure!), but haven't had the time to create and debug a board.

The PCB for this ADSR was got right from this board here. The link was to Thomas's old Midwest site. I modified it a bit to bring it up to the 21st Century version. With permission from Tim Servo, I can post it.
Glad you like my module, I spent a LOT of time getting a consistant design going across my panels, 'cos I want to spend a lot of time with them!

The PCB for this ADSR was got right from this board here. The link was to Thomas's old Midwest site. I modified it a bit to bring it up to the 21st Century version. With permission from Tim Servo, I can post it.
Glad you like my module, I spent a LOT of time getting a consistant design going across my panels, 'cos I want to spend a lot of time with them!

George

Hi George,

Posting a PCB layout here for the ADSR from AS21C is okay by me. I'd just like to ask a few conditions:

1) Please ask before posting a PCB layout from AS21C.
2) Layouts posted here should be for single-sided boards for people who want to etch their own.
3) Layouts must include Thomas' name. Additional text for module description or name would be nice, but is not mandatory.
4) No commercial sales of the layout, parts list, schematic, etched boards or finished modules are allowed.
5) Posting of the schematic is not allowed.

Most of this is common sense, so I really don't anticipate any problems. Magic Smoke is working on a series of boards from AS21C (starting with the Super LFO), but layouts for those who want to etch their own are no problem, and definitely in "DIY Spirit" we have here at E-M. Cheers!

To my knowledge there was no component side for the pcb. If you look closely at the schematic and orient the power pins on each IC then you should be able to figure where every thing goes, thats what I do when the component side is missing.

I can understand your not wanting to spoil it for book purchases. Why not just say that. I believe Thomas has every right to protect his intelectual property, and am a firm believer that every DIYer would benefit from buying his books. I make it a point to buy every one of them I can find as soon as they come to print.

I guess I was just getting lazy, but a little bit of effort on my part is worth it for a Thomas design.

I was looking for an ADSR design and hopefully pcb one day when I came across a link to an archived site, it was Thomas's old Midwest electronics site. The graphics did not show up on my screen at all and somehow I managed to recover this pcb image. I knew it was a Thomas Henry design and I started looking though my pile of reference books and found the circuit in a Thomas Henry article in an old Radio/Electronics, it matched the pcb perfectly, pure luck on my part. So I have the old RE schematic, the pcb image and that was enough to build a great circuit
I guess I should have explained how this pcb came about right from the start.
Just for the record, I never once claimed authorship of this pcb.

In all, My bad. I thought that you had re-designed an old one to fit the new book. Either way, With Ray and Scott's permission, we have an opportunity to build another of Mr. Henry's wonderful design's.

I too have visited the archived remnants of his old site and when I did I felt saddened that it was no longer active. It was with great joy I then later saw Mr. Henry return to the community here on EM. It's a terrible thing, what one person's bad faith can do to a good thing. I also know the sting of it, and must say I don't blame Mr. Henry his reaction at all. I'm just gratified to see him active here, and feel privileged to be able to obtain his writings / designs. I would not want to see anything get in the way of that continuing.

I'm just gratified to see him active here, and feel privileged to be able to obtain his writings / designs.

Ditto here Danno, Thomas Henry more than anyone else has brought this wonderful hobby (obsesion) to me in the most clear and concise way possible. His explanations of the designs are what makes it possible for a person to delve into musical electronics in a safe manner and to learn as we go. I was very happy to see him resurface here and still as productive as ever.

You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot edit your posts in this forumYou cannot delete your posts in this forumYou cannot vote in polls in this forumYou cannot attach files in this forumYou can download files in this forum

Please support our site. If you click through and buy from our affiliate partners, we earn a small commission.